We demonstrate the important role played by non-linear feedback in promoting the fast breakup of the continental lithosphere and the formation of new plate boundaries. We compare the difference in fluid-dynamic and elasto-visco-plastic approaches and emphasize the advection of stresses in finite-element models with large strain Lagrangian formulation. Two types of instabilities were found at multiple time-length scales ranging from 100 years and km scale to 0.1 Myr and 100 km scale. One mechanism relies on the thermo-mechanical elasto-plastic energy conversion, and the other stems from the void-volatile interaction. Elasticity takes on a guiding role in the propagation of shear zones, closely followed by a thermal wave, which is again followed by a wave of volatiles. This last mechanism consolidates the fault zones and establishes the plate boundary for a geological time-scale. Using a fully coupled thermal-mechanical approach, we obtain for the first time a two-dimensional solution, which shows that the constant velocity boundary conditions can lead to episodic avalanche-type tectonic phases within <0.1 Myr. (C) 2000 Elsevier Science B.V. All rights reserved.
Bibliographical noteFunding Information:
We would like to thank Paul Sylvester and the GSA for stimulating this contribution, and we acknowledge Louis Moresi and Hans Mulhaus for very helpful comments. For assistance in graphical design, we would like to thank Christa Lieb, Melanee Lundgreen and Kerri Root. This research has been supported by the ETH Zurich (ETHZ contribution number 1078), the geophysics program of the National Science Foundation and the geosciences program of the Department of Energy.
- Continuum mechanics
- Fluid dynamics
- Plate tectonics
- Shear zones